The experimental work of Versar in producing a condition resembling celiac disease in animals by poisoning with monoiodoacetic acid gave impetus to this clinical study of celiac disease in children and of nontropical sprue in adults. Versar found that his poisoned animals lost the power of absorption of some substances. This loss involved absorption of fats and the products of their digestion, dextrose and galactose. Other sugars and proteins were absorbed normally. The same selective impairment of absorption was found to exist in the patients studied by Dubois. Disturbances of mineral, water and vitamin absorption seem to be secondary rather than primary, with the exception of impaired absorption of riboflavin (vitamin G, or B2). Phosphorylation of riboflavin occurs normally in the intestinal mucosa and is a prerequisite for absorption. This process is definitely impaired both in poisoned animals and in human beings with celiac disease or with nontropical sprue.